The three major problems which are being studied in this project are (1) Studies on the interrelationship of microtubules and the intracellular transport of beta granules using monolayer cultures of islet cells, (2) Studies on the effect of cytochalasin B, alloxan, and certain proteolytic enzymes on insulin secretion, hexose transport and metabolism and the adenyl cyclase system of isolated islets maintained in vitro, (3) Studies on insulin secretion of isolated human islets maintained in vitro.